It very well could be. Fuel pumps are notorious for failing at the gas pump. Another possibility is the vapor recovery system for the fuel tank. I would have the fuel pressure tested and test for trouble codes (DTCs). Learn about your car's fuel system, testing, fuel pressure specifications, and...

Hi Eric.
Scan your vehicle's computer for diagnostic trouble codes (DTCs), this might help you pin down the problem.
If there are no DTCs related to the symptoms, check out the section "What to do when there are no DTCs" for troubleshooting charts and checks. Use the navigation tree...

Hi Sierra.
Have the LeSabre's front and rear suspension checked for loose or worn suspension components for your clunking noise. Check the tires for uneven wear, balance and alignment. There is a technical service bulletin (TSB) that might apply. It is called "Info on popping or thunk noise...